Shelf unit



FIG. 1 is a perspective view of a shelf unit showing my new design;

FIG. 2 is a top plan view, the bottom plan view being identical thereto;

FIG. 3 is a front elevational view, the rear view being identicalthereto;

FIG. 4 is a left end elevational view, the right end being identicalthereto.

The ornamental design for a shelf unit, as shown and described.